CLS CHEM CH 10/11

What are lipids composed of?

Glycerol backbone, 2 hydrophobic fatty acid tails, and a hydrophilic phosphate group.

What does it mean for a molecule to be amphipathic?

It has both hydrophilic and hydrophobic parts.

What are fatty acids?

Linear chains of C-H bonds that end with a carboxyl group.

How are fatty acids classified?

Saturated, monounsaturated, polyunsaturated.

What are the classifications of fatty acids based on the number of double bonds?

Saturated (no double bonds), monounsaturated (one double bond), polyunsaturated (two or more double bonds) between 2 carbons

What are lipids a rich source of?

Energy and an efficient way for the body to store excess calories.

What are the different types of lipids?

Fats and oils (triglycerides), phospholipids, waxes, steroids.

What are triglycerides composed of?

3 fatty acids + 1 glycerol.

How do triglycerides with saturated fatty acids behave at room temperature?

They pack together closely and tend to be solid.

Where do triglycerides with saturated fatty acids come from?

Animal sources.

How do triglycerides with unsaturated fatty acids behave at room temperature?

They form oils.

Where do triglycerides with unsaturated fatty acids come from?

Plant sources (corn, sunflower seeds, and safflower seeds)

Are triglycerides hydrophilic or hydrophobic?

Very hydrophobic + water insoluble (no charged/polar hydrophilic groups)

What are the characteristics of phospholipids?

They contain hydrophobic fatty acid C-H chains and a hydrophilic head group.

How are phospholipids different from triglycerides?

Phospholipids have two fatty acids instead of three, and a phospholipid head.

Are phospholipids amphipathic?

yes

Where are phospholipids found?

surface of lipid layers OR surface of lipoprotein particles

Describe the structure of phospholipids

Polar hydrophilic head OUTWARD towards AQUEOUS environment + Fatty acid chain INWARD away from water

How do phospholipids monitor which molecules can enter/exit the cell?

Size; O2 and H2O can diffuse in/out of the cell while glucose requires transport protein

What is the structure of steroids?

Unsaturated steroid alcohol containing four rings (A, B, C, D) and one C-H side chain tail.

What is the structure of cholesterol?

Unsaturated steroid alcohol with four rings (buried in membrane) and a hydrophilic hydroxyl group on the A-ring (interact w water).

What is found on the surface of lipid layers with phospholipids?

Steroids (cholesterol)

Where are steroids synthesized?

in most tissues from acetyl coenzyme A

Why aren't steroids are source of fuel?

It is not readily catabolized by most cells

How are steroids used in the body?

converted in liver to bile acids that promote fat adsorption in intestine, converted in adrenal gland, testies, ovary to steroid hormones (glucocorticoids/estrogen), transform to vitamin D from sunlight

Since lipids are insoluble in water, they must be transported in association with what?

proteins

What are lipoproteins?

assembly of molecules that transports hydrophobic lipids

What is the structure of lipoproteins?

Triglycerides, cholesterol, phospholipids, and apolipoproteins

Where are cholesterol, phospholipid, and apolipoprotein primarily located?

On the surface of lipoproteins

Where are triglyceride and cholesteryl ester found?

In the core region of lipoproteins

What do larger lipoprotein particles have more of?

Triglyceride and cholesteryl ester + more lipid vs protein > lighter density

Where are apolipoproteins primarily located?

On the surface of lipoprotein particles

What are the different types of apolipoproteins?

APO A1, APO B, APO E

What is the function of apolipoproteins?

Maintain structural integrity, serve as ligands for cell receptors, and activate/inhibit enzymes, allow lipoproteins to bind to lipids

What is the major protein of high-density lipoprotein (HDL)?

Apo A1

What does HDL do?

Removes excess cholesterol from cells and takes it to the liver

Which two levels correlate with each other?

Apo1 rise/fall with HDL

What do deficiencies in apo A1 correlate with?

Increased risk of developing CVD

What are the two forms of Apo B?

Apo B100 and Apo B48

What is the ligand for LDL receptor?

Apo B100

Where is Apo B100 produced/found?

In the liver, found in LDL and VLDL

Where is Apo B48 produced/found?

produced in the intestine, only found in chylomicrons

Function of Apo B48

intestinal fat absorption

Where is Apo E found?

LDL, VLDL, HDL

Function of Apo E

ligand for LDL receptor and chylomicron receptor

What are the three major isoforms of ApoE?

Apo E2, E3, E4

Which isoform of ApoE has an increased risk of developing Alzheimer's disease?

Apo E4

What are the five major classes of lipoproteins?

Chylomicrons, VLDL, IDL, LDL, HDL

Where are chylomicrons produced?

intestine

What is the core structural protein of chylomicrons?

Apo B48

Which lipoprotein is the largest, triglyceride rich, and least dense?

chylomicrons

What is the appearance of postprandial (post-meal) plasma specimens containing chylomicrons?

Turbid or milky

What happens to chylomicrons when stored overnight at 4°C?

They readily float to the top of plasma and form a creamy layer

What is the function of chylomicrons?

transport triglycerides from small intestine and deliver triglycerides to body's cells

How does the size vary between chylomicrons?

High fat meals > Large, fasting state > small

What is the primary site of production for VLDL?

Liver

What are VLDLs primarily composed of?

Apo B100 (core) + triglycerides

What is the function of VLDL?

Transport triglycerides from the liver and deliver them to the body's cells

What is the appearance of postprandial plasma specimens containing VLDL?

Turbid or milky (lipemic)

What is the difference between VLDL and chylomicrons

They do not form a creamy layer because they are smaller and less buoyant

Size of VLDL particles when there is increased production of triglyceride in liver?

Large

What are IDLs also known as?

VLDL remnants

How are IDLs formed?

As VLDL become depleted in triglycerides

What happens to IDLs in the liver?

Returned for reprocessing or made into LDL.

What is the normal presence of IDLs in plasma?

Not typically present in high quantities.

What is hyperlipoproteinemia type III?

Genetic disorder causing body to breakdown fats incorrectly > elevated levels of IDLs in plasma.

How are LDLs formed?

Due to lipolysis of VLDL.

What is the primary component of LDL?

Apo B100 and cholesterol.

What is the function of LDL?

Deliver cholesterol to cells.

How do LDL particles compare to VLDL and chylomicrons?

Significantly smaller.

What can LDL particles do in blood vessel walls?

Infiltrate and contribute to plaque buildup.

What is the significance of LDL particles in cardiac heart disease risk?

May be a better marker for risk.

What are the characteristics of HDL?

Smallest, most dense, synthesized by liver and intestine.

What is the function of HDL?

Remove cholesterol from cells and return to liver.

What are the additional functions of HDL?

Anti-atherogenic, anti-oxidant, and anti-inflammatory.

What are the four major pathways involved in lipoprotein metabolism?

Lipid absorption, exogenous, endogenous, and reverse cholesterol transport.

What is the purpose of the lipid absorption, exogenous, and endogenous pathways?

Transport dietary and hepatic derived lipids to peripheral cells.

Cholesterol in lipid absorption, exogenous, and endogenous pathways vs reverse cholesterol transport?

Cholesterol accumulation can occur VS maintain cholesterol equilibrium

What happens during lipid absorption in digestion?

Pancreatic lipase converts dietary lipids into more polar compounds.

What are the compounds formed during lipid absorption?

Triglycerides > Monoglycerides/diglycerides Cholesterol esters > free cholesterol Phospholipids > lysophospholipids.

What are the aggregates formed during lipid absorption?

Micelles, which are absorbed by intestinal cells.

What happens to absorbed monoglycerides and diglycerides?

Re-esterified into triglycerides and cholesteryl esters.

What happens to newly formed triglycerides and cholesteryl esters?

Packaged into chylomicrons.

What is the exogenous pathway?

Newly synthesized chylomicrons in the intestine enter circulation and travel to peripheral sites.

What does Apo C2 do in the exogenous pathway?

Activates LPL (lipoprotein lipase) in muscles and adipose tissue.

What does LPL do in the exogenous pathway?

It hydrolyzes triglycerides in chylomicrons into free fatty acids.

What happens to the free fatty acids released by LPL in the exogenous pathway?

They are metabolized in muscles and adipose tissue for energy.

What happens to chylomicron remnants in the exogenous pathway?

They are formed and taken up by the liver.

What is the endogenous pathway?

VLDL is formed in the liver from triglycerides and cholesterol esters.

What happens to triglycerides carried in VLDL in the endogenous pathway?

They are metabolized in muscle and adipose tissue by lipoprotein lipase, releasing free fatty acids and forming IDL.

What happens to IDL in the endogenous pathway?

It is taken up by the liver, where triglycerides in IDL are metabolized to LDL.

What can abnormalities in LDL receptor function result in?

Elevation of LDL in the circulation, leading to hypercholesterolemia and premature atherosclerosis.

What is the reverse cholesterol transport pathway?

Pathway for HDL to maintain the equilibrium of cholesterol in peripheral cells.

How is cholesterol transferred from peripheral tissue to HDL in the reverse cholesterol transport pathway?

By ATP-binding cassette transporter ABCA1.

Where does HDL transport cholesterol in the reverse cholesterol transport pathway?

To the liver, where it is excreted via secretion in bile.

What are dyslipidemias?

Diseases associated with abnormal lipid concentrations.

What are some examples of dyslipidemias?

Arteriosclerosis, hyperlipoproteinemia, hypercholesterolemia, hypertriglyceridemia, combined hyperlipidemia.

What is arteriosclerosis?

The thickening of blood vessels due to cholesterol plaque buildup in artery walls.

How are plaques formed?

Lipid deposition > fatty streaks > plaques

What is the main cause of arteriosclerosis?

Lifestyle factors such as diet and lack of exercise, although genetics can also play a role.